Monte Carlo Schemes for Radiative Transfer in Media Represented by Particle Fields

Monte Carlo ray-tracing schemes are developed for the evaluation of radiative heat transfer for problems, in which the participating medium is represented by discrete point-masses, such as the flow field and scalar fields in PDF Monte Carlo methods frequently used in combustion modeling. Photon ray tracing in such cases requires that an optical thickness is assigned to each of the point-masses. Two approaches are discussed, the Point Particle Model (PPM), in which the shape of particle is not specified, and the Spherical Particle Model (SPM) in which particles are assumed to be spheres with constant radiation properties. Another issue for ray tracing in particle fields is the influence region of a ray. Two ways of modeling a ray are proposed. In the first, each ray is treated as a standard volume-less line. In the other approach, the ray is assigned a small solid angle, and is thus treated as a cone with a decaying influence function away from its center line. Based on these models, three different interaction schemes between rays and particles are proposed, i.e., Line-SPM, Cone-PPM and Cone-SPM methods, and are compared employing several test problems.